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authorDongli Zhang <dongli.zhang@oracle.com>2019-03-27 18:36:35 +0800
committerJens Axboe <axboe@kernel.dk>2019-04-10 08:18:25 -0600
commit1978f30a87732d4d9072a20abeded9fe17884f1b (patch)
treedf4d83ad5a1996234900cc4424f413d978eec139 /drivers
parentbf348f9b78d413e75bb079462751a1d86b6de36c (diff)
scsi: virtio_scsi: limit number of hw queues by nr_cpu_ids
When tag_set->nr_maps is 1, the block layer limits the number of hw queues by nr_cpu_ids. No matter how many hw queues are used by virtio-scsi, as it has (tag_set->nr_maps == 1), it can use at most nr_cpu_ids hw queues. In addition, specifically for pci scenario, when the 'num_queues' specified by qemu is more than maxcpus, virtio-scsi would not be able to allocate more than maxcpus vectors in order to have a vector for each queue. As a result, it falls back into MSI-X with one vector for config and one shared for queues. Considering above reasons, this patch limits the number of hw queues used by virtio-scsi by nr_cpu_ids. Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Dongli Zhang <dongli.zhang@oracle.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'drivers')
-rw-r--r--drivers/scsi/virtio_scsi.c1
1 files changed, 1 insertions, 0 deletions
diff --git a/drivers/scsi/virtio_scsi.c b/drivers/scsi/virtio_scsi.c
index 8af01777d09c..f8cb7c23305b 100644
--- a/drivers/scsi/virtio_scsi.c
+++ b/drivers/scsi/virtio_scsi.c
@@ -793,6 +793,7 @@ static int virtscsi_probe(struct virtio_device *vdev)
/* We need to know how many queues before we allocate. */
num_queues = virtscsi_config_get(vdev, num_queues) ? : 1;
+ num_queues = min_t(unsigned int, nr_cpu_ids, num_queues);
num_targets = virtscsi_config_get(vdev, max_target) + 1;